Wire coating apparatus



WIRE COATING APPARATUS 4 Sheets-Sheet l Filed March 7; 1942 0 n 9 u- \2 j rsi n 2 w 5.1!?! VRHI i 9 a A 4 J IHN.. fr n f Tia/El@ A T T ORNE YS Feb. l5, 1944. B M MaCGRGR ET AL 2,341,731

WIRE COATING APPARATUS Filed March '7, 1942 4 Sheets-Sheet 2 Feb. 15, 1944. B, N, M-CGREGQR ET AL 2,341,731

WIRE COATING APPARATUS Patented Pears, 1944 wma ooATlNG APPARATUS Basil N. MacGregor and Robert-0. Scoiield, Warren, h10, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware , Application Marea 7, 1942, serial No. 435,024

s claims. (Gis1-fsa) y This invention relates to an improved wire coating machine and particularly to a machine adapted to coat' the wire by the extrusion process.

It is among the objects of tho present invention to provide a wire coating machinewith extrusion mechanism in which that portion of 'the wire at which the extruded material isapplied is subjected to subatmospheric pressure while the ex terior of the extruded coating material is at. atmospheric pressure so that the coating, applied to the wire, will be uniform in thickness and physical characteristics.

A further object of the present invention is to provide a unitary and compact machine of simple and economical structure and design, capable of transforming a solid coating lmaterial into a plastic or molten condition and for causing said molten material to be forced under pressure into and through an extruder head having provisions for subjecting the bare wire to subatmospheric pressure at a part thereof where a coating of the molten material is extruded around it. s

Further objects and advantages of the present invention will be apparent from the following d escription, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is an elevation of a form of apparatus embodying the present invention, being taken in the direction of the arrow 1 in Fig. 2.

Fig. 2 is a sectional view on the line 2--2 of Fig. 1.

Fig. 3, which is drawn to a larger scale than Fig. 2, is a sectional view of the extruder head and neighboring parts, 3-3 oi Fig. .1. l

Fig. 4 is a fragmentary sectional view showing on an enlarged scale the wire to be coated, the wire guide tube and extruder nozzle.

Fig. 5 is a plan View of the polymer melting grid and is drawn to a larger scale than Figs.1 and 2.

Fig. `6 which is drawn to the same scale as Fig. 5, is a sectional view substantially on the line 5-5 of Fig. 2. l

The apparatus comprises a boiler which com-- prises a horizontal shell 26 welded to a vertical shell 2| -joined to a horizontal shell 22. Shell 2| is welded at its upper end to the flange 23 of a pump and head block 24 having a side extension 25 welded to a spacing ring 26 in turn welded to the shell 22. Obviously," a portion of the upper ,part of shell 2|- must be formed as a separate piece in order that the shell 22 and the block` 24 a section being on the line maybe placed in position, arter which the pieces :f l

are permanently 2631s provided with end walls 21 and 28 (Fig. 1), the latter of which supports a plurality of electrical heating units 23 which project within the boiler.

The block 24 which provides the closure for the upper end 'of shell 2| supports a metal ring Iii from which a helical coil of pipe 3| is suspended, l

' This coil is called the melting grid. The parts 30 and 3| as well aspractically all other parts of `the apparatus excepting, however, the boiler shells 2li and 2| are. made of stainless steel. One end 32 of grid 3| is connected by pipe fittings, 33, 34, 35, 36, 31, 38, 39 and 46 with the lower wall of the boiler shell 20. The boiler receives an initial char e of a heat transfer medium said charge being sufiicient to last for the duration of the longest run ofthe apparatus due to the fact 5 formed between annular metal plates 5| andv 52 that the entire system is closed, with the exception of the grid connections. Various kinds of heat transfer mediums may be used, however, applicant has found that Dowtherm A which is a eutectic mixture of the organic -compounds diphenyl and diphenyl oxide, a well known prody uct, gave very satisfactory results and therefore prefers its use over other well known and widely used heat transfermediums. Some of this heat transfer medium is converted into vapor Within -the boiler to heat the block 24 and the extruder' head to be described. Some of the vapor ows out through pipe 4| (Fig. l) and into the melting grid 3| through pipe 42 where heat is .given off to melt the solid polymer which descends from a hopper above, to be described. The vapor condensed in the grid 3| returns to the boiler through l the pipe connections 32 to 40.A

A ring oi good heat insulating material is and is bound together by a metal sleeve 53. The

ring 15|) supports an aluminum flange 54 attached to an aluminum tube providing a hopper-for receiving solid particles of the polymer to be melted. 'Ihe flange 54 receives semi-annular -clamping members 56 and 51. The parts 56, 51.

54, 50 and 36 aresecured to the ange23 of block 24 by clamping screws 58 and 59.

The hopper tube which is about 9 inches inside diameter and about 4 feet long extends upwardly from its supporting ange 54 and is provided at its upper end with an aluminum flange 60 which supports a metal ring 6| having an annular boss 62 which receives a ring 63 which secures a onehalf inch' glass disc 64 withina metal ring 65 provided with a plurality of notched lugs 66, eachv for receiving a screw 6l pivotally attached at 68 secured by welding. The shell filled1 with grains or particles of to the ring 6| and threadedly engaged by a winged nut 69 the tightening of which causes the ring 63 to be compressed between the glass and the annular boss 62 of the ring 6|. Bolts 60h and half-rings 60a secure the ring 6| to the flange 60.

Since the polymer must be melted under nonoxidizing conditions, air is excluded by introducing an inert gas, such as nitrogen, through the inlet 10 at pressure slightly above atmospheric. This gas may ow out through a pipe 1|, the lower end of which opens into an annular space 12 between the sleeve 53 and an aluminum baille sleeve 1S suspended from the aluminum ring 5d. 'I'he hopper lid 65 being removed, the hopper is polymer in solid form. The-lower end of the stack of polymeer grains is supported byo the melting grid 3| and is spaced from the heat insulating ring by the bathe sleeve i3. The polymer is melted by the heat of the melting grid 3i; and themelted polymer occupies the pot 14 provided by the block 24. The pot 14 has an'outlet 15 plugged at 16 and connected with passage l? which is the inlet of a pump 10 secured to the block 24 as shown in Fig. '6. The outlet 19 of pump 10 is connected with passage 80 plugged at 6| (Fig. 2). Passage 80 is connected with inlet passage 82 of pump 83 having an outlet passage 84 connected with passage 85 to the extruder head, to be described.

As shown in Fig. 6, the shaft'90 of pump 19 has a sprocket 92 operatively connected to any drive shaft (not shown) by a chain 93. Another sprocket 9d on shaft 90 is drivingly connected to a sprocket 95 through chain 95a, sprocket 95 being secured to the shaft 9| of pump d3. Due to ythe fact that during the melting operation there are certain entrapped gases in the molten polymer, one pumpl is driven at a greater speed than the other. As a result of such diierential pump operation these gases are compressed between the pumps which either forces them out or breaks them up into such minute quantities as to make them insignificant to the operation. Thus the sprockets 92, 94 and 95 are ofsuch relative size that pump 83 operates at a slower speed than pump 18. Although the diiierential of pump operation is substantially constant,` as for instance7 R. P. M. the operating speeds of the pumps are varied in accordance with the size of the wire being treated, the thickness of the coating applied to the wire and the speed at which the wire traverses the machine.

In Fig. 6 the dot dash circle 14 represents the largest diameter of the pot 14 shown in Fig. 2. The smaller circle 14a represents the small diameter at the bottom leading to the outlet 15. In

Fig. 6 the passagesfrom the pot through the pumps to the extruder head can readily be traced. The lower portion of the block 24 is provided with anenlargement 90 having a recess 91 for receiving the extruder head block clamped in the position shown by a tubular nut |0| and located by a dowel pin |02 (Figs. 2 and 3). Block |00 lis provided with a horizontal bore |03`closed at its right end byi a plug |04 having a central bore |05 for receiving a heat measuring instrument which may be provided with a threaded exterior to tit into the screw threads at |06. The left end of bore |03 flares out at |01 into a recess |08 which receives a strainer unit comprising a shell |09 enclosing strainer material ||0. A gasketring is located between the shell I 09,.and the block tween the shell |09 and the extension of block loo, and a gasketuz is located be? amai . The passage |03 through the block |00 is intercepted by a vertical bore ||5 connected at its upper end with a counterbored recess I6 and at its lower end with a counterbored recess |1. The bore ||5 receives a wire guide tube ||8 threaded y at ||9 at its upper' end for receiving a nut |20 head is encased in which, by contacting the surface 2 of recess H6, serves as a stop-for limiting the downward movement'of the tube 8, thereby determining the position of the conical lower end portion |22 of the tube H8 with reference to .a block |23 having an internal conically tapered surfacer |24. The block |23 is located in the recess ||1 and a sealing gasket |25 is located between the block |23 and the block |00. Block |23 is secured in position by a nut |26 engaging the screw threads |21 provided by a wall of the recess ||1. The tapered lower end |22 of guide tube H8 cooperates with the tapered internal surface |24 of block 23 to provide an annular conically tapered passage |30 through which the melted polymer is forced and is caused to envelope the wire W which passes downwardly through the guide tube H8. The width of this passage is especially critical and must be varied in accordance with the size of the wire being treated. lThe tube ||8 is held in the desired position of adjustment by ,screwing against its upper end a nut |3| cooperating with the threads |32 of a wall of the recess H6. While turning the nut |20 in order to produce relative movement between the nut and the tube H8, the latter is prevented from 'turning by reason of a pin |33 extending therefrom into a longitudinal slot |34 in block |00. l

The nut |3| supports a tube 40 threaded at its upper end to receive a nut |4| having a shoulder |42 which clamps a rubber or felt washer |43 in position. The washer is centrally apertured with a hole slightly smaller than the wire W so as to rub against the wire with sufficient pressure to provide a seal. The tube 40 is provided with-a side fitting |45 to which a pipe connected with a vacuum pump may be attached. During the operation of the machine the interior of the tube |40 is subjected to subatmospheric pressure so that the bare portion of the wire W at the truder head, it passes through a sleeve |5| also Welded to the shell 22 and block extension 96.

Since the block 24 is contained within the boiler. said block and thek extruder head are maintained at a temperature above the melting point ofthe polymer. In order to reduce heat loss', the boiler is enclosed in a sheath of nonconducting material |60 enclosed in a metalA jacket ISI. The right-hand side of the extruder a pad |62 of non-conducting material. In Fig. 1 the insulating enclosure |60 is represented by a dot dash line. Upon the upper end of thesheath |60 there are placed two half rings of head insulating material |03.

As shown in Fig. 1 the pumps 18 and 83 are located within a recess |10 'set into the boiler and bounded by plates |J| and |12 and by the acusar J 3 being treated and the thickness of coating being applied. However under'certain circumstances this machine has been operated with a pressure of approximately 500 pounds per square inch between the Apumps and av temperature of about 590 F. within the boiler and at the melting grid.

The value of the subatmospheric pressure in tube 140 averages about 2 inches of mercury. The

linear speed of the wire is entirely governed by the size of the wire and the thickness of the coating applied thereto. No preheating of the wire or care is necessary in this apparatus.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as'followsf 1. A wire coating machine comprising in combination, a supply means for a viscous material; a heating unit therefor; an extrusion nozzle having a hollow core providing a wire guide throughwhich. the wire moves to pass the mouth of the nozzle; conduits connecting the supply means and nozzle; pumps in heat transfer relation with the heating unit and in communication with said conduits for forcing the material through the nozzle onto the-wire, said heating unit also heating the nozzle and the coating material passing therethrough.

2. A wire coating machine comprising in combination, a supply hopper containing a coating material; a grid through which` the material passes; a heating unit connected to said grid 'to render the coating material viscous; an extrusion nozzle, heated by the heating unit, and having a hollow core providing a wire guide; means in heat transfer relation with said heating unit, for forcing the viscous coating material through i the extrusion nozzle onto the wire passing through the core a pot for receiving the viscous material; and conduits connecting the pot with ssliid forcing means and said means with the nozz e.

3. A wire coating machine comprising in combination, a supply hopper containing a coating material; a grid through which the material passes; a heating unit for said grid to render the coating material viscous; a pot into which said lviscous material passes; an extrusion nozzle,

heated by the heating unit, and having a hollow core providing a wire guide; means in heat trans.-

ing means with the nozzle; and means providingv a differential pressure on each side of the opening of the wire guide .through lwhich the wire passes and enters the mouth of the nozzle whereby the viscous material is urged into intimate contact with the surface of the wire and be of uniform thickness.

5. A wire coating machine comprising in cornbination; 'a supply means for a viscous coating material; an extrusion nozzle providing a wire v guide through which the wire is moved to pass coaxially through the mouth of the nozzle; means for forcing the material through the nozzle onto the passing wire; pipes connecting the supply means. the forcing means and the extrusion nozzle; and means providing a subatmospheric pressure within the wire guide and at the point in the nozzle when the coating material is applied to the wire whereby the inner surface of the extruded material is subjected to subatmospheric pressure while the exterior surface thereof is subjected to atmospheric pressure causing the material to be urged into intimate contact with said passing wire.v

6. A wire coating machine comprising incombination, a supply means for a viscous coating material; an extrusion nozzle comprising a block having a passage with a restricted opening and a hollow core in said passage, one end of the core cooperating with the restricted opening of the passage to provide an extrusion orifice, the hollow core providing a wire guide for passing the wire concentrically through the extrusion orifice; a pump for forcing the viscous material through the nozzle onto the passing wire; conduits connecting the supply means with the pump and the pump with the nozzle; and means providing a differential pressure on each side of the opening in the wire guide through which the wire passes to the nozzle orifice whereby the viscous material is pressed circumferentially into y intimate contact with the surface of the wire and be of uniform thickness.

'1. A wire coating machine comprising in combination, a supply means for a viscous coating material: an extrusion nozzle comprising a block having a passage with a restricted opening land a hollow core in said passage, one end of the core cooperating with the restricted opening of the passage to provide an extrusion orifice,. the hollow core providing a wire guide for passing the wire concentrically through the extrusion fer relation with said heating unit, for forcing the viscous coating material through the extrusion nozzle onto the wire passing through the core; conduits providing communication lbetween the pot and forcing means and said forcing means and nozzle; and means for providing a subatmospheric pressure around the wire within A the confines of the nozzle core forming the wire orifice; a conduit connecting the supply means with the nozzle; a pump connected to said conduit for forcing the viscous material through the conduit into the nozzle and onto the passing wire; and means providing a subatmospheric pressure within the wire conducting guide which tends to draw the material, forced under pressure into the extrusion nozzle, toward'the interior of said guide. through which the wire is constantly passing in the opposite direction,

vwhereby said viscous material is air pressed into intimate contact with said wire. l

8. A wire coating machine comprising in comf bination, a boiler; heating ymeans within the boiler; a medium in said boiler which, when heated, is transformed into hot vapor; a head block in said boiler, heatedby the vapors therein, and provided with a receiving chamber; a hopper in communication with -said receiving chamber, said hopper containing the supply of wire coating material; a grille between the hopper and receiving chamber and connected by pipes with the boiler, said grille being heated by the vapors connected to said conduits for forcing `the viscous l0 covering material through the conduits and the nozzle onto the wire passing therethrough; and

means providing a pressure in the wire guide, lower than the pressure outside said guide whereby said diierential pressures will urge the covering material into intimate contact with the wire as it moves from the guide through the mouth of the nozzle.

BASIL N. MAGGREGOR. ROBERT 0. SCOFIELD. 

